This proposed work is designed to elucidate the biochemical and/or physiological mechanisms in the brain mediating the regulation of food intake of animals fed disproportionate amounts of dietary amino acids. Our objective is to determine the location and the nature of the critical neural and/or other areas known to affect feeding behavior and the mediator, metabolic or otherwise, as well as the mode through which the control mechanism is triggered in response to dietary or experimental changes involving protein, amino acid, or other nutrients in disproportionate amounts. To achieve this goal, we intend to identify or establish the effects of injection or infusion either peripherally or centrally (through acute or chronic implant cannulas) of certain amino acids, neuropeptides, or certain drugs on the changes in feeding responses of normal rats or rats with lesions in critical neural areas, fed amino acid imbalanced or devoid diets or diets containing excessive quantities of protein or amino acids. Also, the changes in detailed feeding patterns will be determined with a computerized feeding monitoring system, and closely correlated with changes in biochemical and/or physiological parameters in plasma, brain or certain areas of the brain, cerebral spinal fluid or other tissues under conditions in which the food intake regulation mechanism is activated by dietary or other treatments or exogenously introduced substances as mentioned. Also, ablations of the extrahypothalamic areas (such as the area postrema and others) will be carried out to characterize the involvement of these areas in food intake regulation of animals fed disproportionate amounts of dietary amino acids. Thus far no system in the brain has been found that is responsive to excess dietary protein or amino acids. This should provide a better understanding of the mechanism mediating the food intake regulation of animals and men under conditions of disproportionality of dietary protein and amino acids.